Rendering over repaired damp problem

[daz3770]

Hi there gents,

I have hacked the plaster off the lower part of my wall and cleared the bridging that caused the damp initially. It has been drying for about 6 weeks now.

What I need to know is what steps i need to take now, as to whether I need to apply anything to the wall before rerendering?

Also what products should i use to make up the render? Would it be builders sand and cement 4:1 or something else? Do i need to add anything else to the mix?

Many thanks

 

[noseall]

you need to use plasterers sand and cement, and you need to use a waterproofer/plasticiser in the mix.

 

[daz3770]

thanks for you help, kind regards

 

[spongey]

pva your walls to kill the suction then use hardwall mate. it easier to prepare and use than render and is just as good in my opinion.

if you are insistant on using render then use sharp sand (i have never heard of plasterers sand) and the ratio i use use 4:1 sand, cement and a little waterproofer/plasticiser.

you will need to do a scratch coat 10mm approx then top coat 10mm approx and finally rub it down to level the hollows.

u will also need a featheredge or long straightedge to rule of and regularly check for levelness as you cant rectify seriously uneven walls with multi finish later.

 

[dougalhouse]

FYI : Plastering sand is available from good merchants and is generally a finer sand than sharp which is used in screeding and is a bugger to rub up if used for rendering.

 

[spongey]

no offence meant dougal just stating never heard it called plasterers sand.

i asked a few of the lads this morning about it but none of them heard of it either.

is it soft sand? who produces it? which merchants is it available from?

i would like to know cos if its easier to use than sharp i will give it a try!

 

[Micilin]

no offence meant dougal just stating never heard it called plasterers sand.

i asked a few of the lads this morning about it but none of them heard of it either.

is it soft sand? who produces it? which merchants is it available from?

i would like to know cos if its easier to use than sharp i will give it a try!

Fine sharp, 3mm down, washed, salt free.

"Leighton Buzzard" a classic sand round our way.

Sharp sand is usually 6mm down.

 

[dougalhouse]

None taken Spongey

In and around London we used to use Leighton Buzzard sand as Micilin said available Erith's or Travis Perkins

Down here I use Jewsons, Travis Perkins or Sydenhams and just specify 'Plastering sand'

Make sure when you order it the guy knows exactly what you want, like when trying to order Thin coat stops

And yes it's a dream to use especially when you chuck in a bit of lime in the floating mix.

 

[olneys]

Hello chaps

Could I just ask a couple of questions related to this post?

- Do you use pva\water on the brick work if you use the sand\cement render method to reduce the suction as you would with applying hardwall?

- If you use hardwall instead of the sand/cement, do you apply in the same manner, ie apply a scratch and float coat?

thanks for your extra advice

olneys